FULLERENES COUNTERACTING ORGANOPHOSPHORUS THREATS. Nerve agents used as agents of terror include organophosphorus (OP) compounds, neurotoxic substances that inhibit acetylcholinesterase (AChE) activity. When the neurotransmitter acetylcholine is not destroyed cholinergic poisoning can result. Contemporary treatment relies on blocking cholinergic receptors, removing OP compounds from AChE, and treating symptoms. This is often incomplete in poisoning with the potent and rapidly acting OP nerve agents, so additional countermeasures are desired. Our preliminary data show water soluble hydroxylated C60 fullerenes (C60-OH) have ability to decrease AChE inhibition in neuronal cells. Our preliminary data show no overt toxicity in mice after IV injection of a soluble C80-OH metallofullerene Trimetasphere[unreadable]. These data suggest in vivo potential of soluble fullerenes to safely detoxify OP toxicants. C60/C80-OH fullerenes and other soluble derivatives also have antioxidant properties likely to be useful against the oxidative stress associated with excitotoxicity resulting from rapid and life-threatening AChE depletion, effects that can be long-lasting and/or delayed and, when unopposed, contribute to neuropathy. Therefore, based on our preliminary data, the hypothesis is that soluble C60/C80-OH and other derivatives can decrease capability of OP compounds to inhibit AChE and also counteract oxidative effects. We predict that soluble C60/C80 derivatives can be safely administered as OP antidotes, either alone or in combination with currently accepted treatments (IV atropine, pralidoxime, diazepam). We propose to examine the ability of soluble C60/C80 derivatives to interact with OP nerve agent surrogates (DFP, paraoxon). Initial screening will be done in vitro by evaluating non-cytotoxic soluble C60/C80 derivatives for their ability to decrease OP-induced effects, including AChE inhibition, in neural tissue and neuronal cells. Using the best-performing compounds from the in vitro studies, experiments using mice will validate in vitro findings, examining the effectiveness of soluble C60/C80 derivatives as ameliorators of OP-induced effects on behavior, AChE inhibition, and brain neurochemistry and structure when given alone or in combination with traditional treatments. Successful identification of safe and effective fullerenes which have both AChE-protection and antioxidant properties will provide potential to protect and treat acute and delayed effects of nerve agent poisoning.